Lets hope the setup was a freebie. If not bring ti back and tell him what's not to your liking.
Are ALL frets buzzing ? Then there are a few things to look at.
- The Epiphone bridge has a wire retaining saddle screws. It can rattle. If so, you could try bending down the wire. With a flat screwdriver, bend it a tad downwards between screws. Doesn't need much.
- The nut could be the culprit for buzzing. Probably is for wrecking the tuning. That nut needs to be cut better and maybe lubricated.
- If strings are loosely wrapped around tuner posts, they will become loose and detune.
- Make sure you stretch those new strings you just put on.
- Wrap lock them like this.